Permafrost isn't necessarily permanent.
A new NASA study looked at the frozen soil layer in the coldest reaches of the northern Arctic and found it could "thaw enough to become a permanent source of carbon to the atmosphere in this century."
This comes as a surprise since scientists previously thought the cold, remote areas of the arctic would be less vulnerable to climate change and take longer to become a significant carbon source (rather than remaining carbon-neutral) than the Arctic's warmer, more southerly regions.
The Arctic permafrost, located beneath the topsoil layer, has remained frozen for long stretches of time, but it holds a stash of organic materials, including leaves. When it thaws, that material breaks down and releases methane and carbon dioxide greenhouse gases. These gases, which are also generated by human activities, can contribute to global warming.
NASA Jet Propulsion Lab scientist Nicholas Parazoo led the study, which involved running model simulations that calculated changes in carbon emissions, plant growth and permafrost due to a warming climate.
"Over the course of the model simulations, northern permafrost lost about five times more carbon per century than southern permafrost," NASA says of the research, which appears in the journal Cryosphere.
The warmer southern areas of the Arctic are already experiencing some permafrost thaw, but this region's carbon footprint will likely be offset by plant growth. The study shows increased photosynthesis from plants will balance the southerly emissions until the late 2100s.
NASA has expressed concern about permafrost thawing before. "Climate change is already happening in the Arctic, faster than its ecosystems can adapt. Looking at the Arctic is like looking at the canary in the coal mine for the entire Earth system," NASA research scientist Charles Miller said in 2013 while working on the agency's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) project.
The new study estimates that "as thawing continues, by the year 2300, total carbon emissions from this region will be 10 times as much as all human-produced fossil fuel emissions in 2016."
Should we be worried? The key findings, Parazoo says, are that the cold northern Arctic will transition into a net carbon source earlier than expected, but it won't likely become a substantial source of carbon for a couple centuries. "However, the region should be closely monitored due to the large amount of vulnerable carbon," he says.
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